The present invention falls in the technical field of edible spread processing and relates to a process for the preparation of edible spreads and to an apparatus for carrying out this process.
It is commonplace to use "Votator" (RTM) units in edible fat processing. These comprise both "A-units" and "C-units".
A-units, serve both to cool and crystallise an emulsion, whereas C-units, while also being used for crystallisation are also used to apply sufficient shear to induce phase inversion of a oil in water emulsion or premix to a water-in-oil dispersion. In spread manufacture by the phase inversion process, it is commonplace to separate the cooling and inversion steps, such that cooling occurs in one or more A-units in line, prior to a C-unit which functions as an invertor.
Our previous European patent EP 98664 discloses a process for producing a water-in-oil emulsion spread having a fat content of at most 60%, wherein an emulsion containing oil and water is both sheared and cooled in an apparatus internally coated with a layer of hydrophobic material selected from the group comprising PTFE and butter oil. In this process, fat flushing may be employed prior to start-up, so as to form the hydrophobic coating. No phase inversion occurs in this process.
European patents EP 98664 and EP 40874 both disclose the general process of fat-flushing prior to continuous process operation. In this process fat is first circulated through the process line and a cream is introduced until the required process conditions are attained. Again, this is not a true phase-inversion process.
It is difficult to maintain inversion with low fat levels especially if fats with high solids are being used. Problems in maintaining inversion are also caused when the process stream includes certain ingredients. Without wishing to restrict ourselves to any particular theory of operation, it is believed that the presence of, for example, oleaginous milk powders and other polar materials, in the process stream, hampers the inversion process. Such powders are considered important ingredients in edible spreads as they modify the organoleptic and physical properties of the products obtained.
Failure of the inversion process results in so-called "cold-flushing" of the process line resulting in production of a microbiologically unstable, and organoleptically unacceptable product. Cold flushing occurs when phase inversion fails to occur. Inversion may only be recovered by stopping and restarting the process which results in plant down-time and can result in loss of materials. The risk of inversion failure at a particular throughput often determines the maximum production capacity of a spread manufacturing line.
A further limitation on the capacity of some spread processing lines is the volume of product which may be packed in unit time. Products cannot normally be stored before they are packed and therefore the capacity of the packing apparatus is often a rate determining factor. There would be a great advantage in being able to double the throughput of a line as this would make it possible for a single line to serve two packing machines of the same capacity, and therefore to double capacity at the cost of a single packing machine.